[amsat-bb] Re: USB-to-Serial adapter

[Sil - ZL2CIA]

Norman,

My experience is that some of the really cheap ones don't have proper 
level shifters on the RS232 (V.24) side. Instead, they use "power 
stealing" from the RS232 line. This doesn't always work.

It certainly won't work if the TTL <--> RS232 level shifter you use to 
connect to the rig also tries to "power steal"

There is another option. I see RS232<-->USB converters sold here that 
use 3.3 and zero volt levels, rather that -12 and +12 volt on the RS232 
side. Since you are building you own interface, you could use these 
instead. From memory, the FT736R uses inverted signals on the TTL side, 
so one TTL inverter chip would probably be all you needed (oh, plus a 
7805 or similar)


Sil

ZL2CIA

Norman W Osborne VE3CJE wrote:
> Hello everyone,
>
> I am building an interface for a 736r doppler control and I will be needing
>
> a USB-to-Serial adapter.
>
> Looking on ebay I see many choices and prices.
>
> Have any of you bought any of these adapters??
>
>  
>
> Any suggestions appreciated.
>
>  
>
> 73,
>
> Norman.
>
>  
>
>  
>
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